1. Field of the Invention
The invention relates to a Double-Layer Super Twisted Nematic(DSTN) display with electromagnetic shielding.
2. Description of the Prior Art
The active cells of a DSTN display have two transparent plates (for example made of glass or plastic) arranged at a distance from one another. Transparent electrodes are fitted on the surfaces of the sides of the plates that are assigned to one another, a liquid crystal substance being arranged between said electrodes. Depending on the applied voltage, the liquid crystal substance changes the plane of polarization of the light penetrating through the liquid crystal substance. Outside the liquid crystal, a total of two pole filters are arranged in the beam path of the light penetrating through the liquid crystal cell, which filters transmit light only in one plane of polarization. Thus, the light beams are transmitted or blocked depending on the position of the pole filters with respect to one another and the driving of the electrodes, with the result that a correspondingly driven pixel of the display appears dark or bright.
For the improvement of the image quality, DSTN cells also include a passive cell arranged in the beam path of the light the passive cell includes a liquid crystal substance likewise arranged between two transparent plates and has an opposite modular orientation in contrast to the liquid crystal substance of the active cell.
The driving of the individual pixels gives rise to electromagnetic interference on account of the high driving frequencies that occur in this case, which electromagnetic interference can penetrate toward the outside unimpeded if no countermeasures are implemented. Furthermore, in particular in the context of use in motor vehicles, in the case of a user of the motor vehicle, due to friction between the user's clothing and cover materials of the motor vehicle seats or the seat belts of the motor vehicle, the user may be charged to high static voltages. If a part of the user's body then comes in proximity to the display, voltage flashovers may occur which may damage or even destroy the display. Therefore, it is known from the prior art to provide a metal frame for protecting the display, but the metal frame is an additional component and is complicated and expensive to produce.